Sentaurus Structure Editor
3. Generating Doping Profiles

3.1 Defining Constant Doping Levels in Materials
3.2 Defining Constant Doping Levels in Regions
3.3 Defining Analytic Doping Profiles
3.4 Saving the Model
3.5 Assignment

Objectives

• To introduce the most important 2D doping definitions of Sentaurus Structure Editor using an SOI MOSFET.

3.1 Defining Constant Doping Levels in Materials

In this section, the SOI MOSFET built in Section 2. Generating 2D Boundaries will be used.

First, the most basic approach to defining a constant background doping level within a material type is introduced.

To introduce a constant boron background doping of 1 x 10¹⁵ cm^-3 in the silicon material:

1. Device > Constant Profile Placement.
   The Constant Profile Placement dialog box is displayed.

   

   Figure 1. Constant Profile Placement dialog box.

2. Type the name PlaceCD.Silicon in the Placement Name field.
3. In the Placement Type group box, select Material, and select Silicon as the region name.
4. In the Constant Profile Definition group box, type Const.Silicon in the Name field.
5. Select BoronActiveConcentration from the Species list.
6. Enter 1e15 in the Concentration field.
7. Click Add/Change Placement to add the doping to the silicon substrate region.
8. Click Close.

The assignment of a constant doping profile to a specific material type involves, in general, two steps.

The first step is to define a constant profile, which in this case requires all the fields in the Constant Profile Definition group box to be completed.

The second step is to associate the defined profile with a material type, which is performed by Sentaurus Structure Editor when the Add Placement button is clicked. However, before this last step, both the placement type and material type in the Placement Type group box must be selected.

The corresponding Scheme commands that reflect these two steps are:

(sdedr:define-constant-profile "Const.Silicon" "BoronActiveConcentration" 1e+15)
(sdedr:define-constant-profile-material "PlaceCD.Silicon" 
  "Const.Silicon" "Silicon") 

3.2 Defining Constant Doping Levels in Regions

The placement of a constant doping profile in a material adds the profile to everywhere the specified material resides. This may include more than one device region. Alternatively, a doping profile can be assigned to only selected device regions.

To dope the silicon epilayer with a uniform boron concentration of 1x10¹⁷ cm^-3:

1. Device > Constant Profile Placement.
   The Constant Profile Placement dialog box is displayed.
   

   

   Figure 2. Constant Profile Placement dialog box.

2. Type PlaceCD.Epi in the Placement Name field.
3. In the Placement Type group box, select Region, and select R.Siliconepi as the region name.
4. In the Constant Profile Definition group box, type Const.Epi in the Name field.
5. Select BoronActiveConcentration from the Species list.
6. Enter 1e17 in the Concentration field.
7. Click Add Placement.
8. Click Close.

The corresponding Scheme commands are:

(sdedr:define-constant-profile "Const.Epi" "BoronActiveConcentration" 1e17)
(sdedr:define-constant-profile-region "PlaceCD.Epi" "Const.Epi" "R.Siliconepi")

Constant doping profiles also can be applied to an evaluation window by selecting Ref/Win in the Placement Type group box. (See Section 4.3 Defining Refinement Windows for instructions to define an evaluation window.)

3.3 Defining Analytic Doping Profiles

In Sentaurus Structure Editor, doping profiles characterized by analytic functions, such as Gaussian and error functions, can be defined. In addition, Sentaurus Structure Editor allows you to define doping profiles of your own functions, which can be useful in some applications.

The placement of an analytic profile is, in general, performed in two steps. The first step defines the baseline and the second step defines the shape of the profile itself. The baseline is used to determine the lateral extent of the profile and can also serve as the reference point for the depth of the peak position.

Two Gaussian doping profiles are to be added to the source/drain and their extension regions of the example structure. For the source/drain region, the target is a Gaussian phosphorus profile with a peak concentration of 5 x 10¹⁹ cm^-3, a junction depth of 0.12 μm, and a lateral straggle/diffusion factor of 0.8.

For the source/drain extensions, the goal is a Gaussian arsenic profile with a peak concentration of 5 x 10¹⁸ cm^-3 and a junction depth of 0.035 μm.

Auto Region-Naming Mode: By default, Sentaurus Structure Editor automatically assigns names such as RefEvalWin_1 and RefEvalWin_1 to newly created reference windows such as baselines. This is useful in some applications but, in most cases, you may prefer to use your own names, which are more descriptive and easier to remember.

To switch off the auto region-naming mode:

• Draw > Auto Region Naming, and clear this mode.

When the mode has been switched off, you will be prompted to enter the name whenever a new baseline is created.

To define the baseline:

1. Mesh > Define Ref/Eval Window > Line.
2. In the view window, click the first point of the baseline.
   The Exact Coordinates dialog box is displayed.
3. Enter (-0.8 0) for the start point, and click OK.
4. Click again to define the end point of the baseline.
5. Enter (-0.2 0) for the end point, and click OK.
6. In the displayed dialog box, enter the name BaseLine.Source for the baseline, and click OK.

Similar steps can be repeated to define the drain-side baseline and the baselines for the source and drain extension junctions.

Use the following baseline names and the start and end locations.

Junctions	Baseline name	Start point	End point
Source	BaseLine.Source	(-0.8 0)	(-0.2 0)
Drain	BaseLine.Drain	(0.2 0)	(0.8 0)
Source extension	BaseLine.SourceExt	(-0.8 0)	(-0.1 0)
Drain extension	BaseLine.DrainExt	(0.1 0)	(0.8 0)

The corresponding Scheme commands are:

(sdedr:define-refinement-window "BaseLine.Source" 
  "Line" (position -0.8 0.0 0.0) (position -0.2 0.0 0.0))
(sdedr:define-refinement-window "BaseLine.Drain" 
  "Line" (position  0.2 0.0 0.0) (position  0.8 0.0 0.0))
(sdedr:define-refinement-window "BaseLine.SourceExt" 
  "Line" (position -0.8 0.0 0.0) (position -0.1 0.0 0.0))
(sdedr:define-refinement-window "BaseLine.DrainExt" 
  "Line" (position  0.1 0.0 0.0) (position  0.8 0.0 0.0))

To define and place an analytic doping profile:

1. Device > Analytic Profile Placement.
   The Analytical Profile Placement dialog box is displayed.

   

   Figure 3. Analytical Profile Placement dialog box.

2. Type PlaceAP.Source in the Placement Name field.
3. Select the baseline BaseLine.Source from the Ref/Win list.
4. In the Profile Definition group box, enter Gauss.SourceDrain in the Name field.
5. Select Gaussian from the Profile Type list and PhosphorusActiveConcentration from the Species list.
6. In the Primary Direction Profile (Gauss) group box, type 5e19 in the Peak Concentration field and 0 in the Peak Position field.
7. Type 1e17 in the Junction field and 0.12 in the Depth field.
8. In the Lateral Direction Diffusion group box, enter 0.8 in the Factor field.
9. Click Add Placement.
10. Repeat all steps for the drain junction profile and the source/drain extensions.

Similar steps can be executed to assign the drain junction profile and the profile for the source/drain extension junctions. Use the following listed profiles accordingly.

Junctions	Placement name	Baseline name	Profile name
Source	PlaceAP.Source	BaseLine.Source	Gaussian.SourceDrain
Drain	PlaceAP.Drain	BaseLine.Drain	Gaussian.SourceDrain
Source extension	PlaceAP.SourceExt	BaseLine.SourceExt	Gaussian.SourceDrainExt
Drain extension	PlaceAP.DrainExt	BaseLine.DrainExt	Gaussian.SourceDrainExt

The Gaussian profiles are defined as follows.

Profile name	Peak concentration	Peak position	Junction concentration	Junction depth	Lateral factor
Gaussian.SourceDrain	5x1019 cm-3	0 μm	1017 cm-3	0.12 μm	0.8
Gaussian.SourceDrainExt	5x1018 cm-3	0 μm	1017 cm-3	0.035 μm	0.8

The corresponding Scheme commands are:

(sdedr:define-analytical-profile-placement "PlaceAP.Source"
  "Gauss.SourceDrain" "BaseLine.Source" "Positive" "NoReplace" "Eval")

(sdedr:define-gaussian-profile "Gauss.SourceDrain"
  "ArsenicActiveConcentration" "PeakPos" 0.0 "PeakVal" 5e19
  "ValueAtDepth" 1e17 "Depth" 0.12 "Gauss" "Factor" 0.8)

(sdedr:define-analytical-profile-placement "PlaceAP.Drain"
  "Gauss.SourceDrain" "BaseLine.Drain" "Positive" "NoReplace" "Eval")

(sdedr:define-analytical-profile-placement "PlaceAP.SourceExt"
  "Gauss.SourceDrainExt" "BaseLine.SourceExt" "Positive" "NoReplace" "Eval")

(sdedr:define-gaussian-profile "Gauss.SourceDrainExt"
  "ArsenicActiveConcentration" "PeakPos" 0.0 "PeakVal" 5e18
  "ValueAtDepth" 1e17 "Depth" 0.035 "Gauss" "Factor" 0.8)

(sdedr:define-analytical-profile-placement "PlaceAP.DrainExt"
  "Gauss.SourceDrainExt" "BaseLine.DrainExt" "Positive" "NoReplace" "Eval")

The profile definition for the contact and extension profiles can be used for both the source and drain implants.

3.4 Saving the Model

To save the model, follow the instructions in Section 2.14 Saving the Model.

Figure 4. Device with its latest doping conditions.

Click to view all the commands discussed in this section in the command file doping_dvs.cmd.

The complete project can be investigated from within Sentaurus Workbench in the directory Applications_Library/GettingStarted/sde/soifet.

3.5 Assignment

Create the doping profile definitions for the SiGe HBT from Section 2.15 Assignment.

Figure 5. SiGe HBT with its latest doping conditions.

Click to view a solution of the command file sigehbt_dvs.cmd.

The complete project can be investigated from within Sentaurus Workbench in the directory Applications_Library/GettingStarted/sde/sigehbt.